Tooth back plate for artificial teeth



April 28, 1931- M. DE TERRA TOOTH BACK PLATE FOR ARTIFICIAL TEETH Filed July 26, 1929 &

3'77. (/2 dab KM Patented Apr. 28, 1931 PATENT OFFICE MAXIMILIAN DE TERRA, OF ZURICH, SWITZERLAND TOOTH BACK PLATE FOR ARTIFICIAL TEETH Application filed July 26, 1929, Serial No.

The present invention relates to a tooth back plate for sets of artificial teeth and to a process for making such plates.

In the back plates hitherto known for exchangeable teeth, which are made as a whole in gold of high purity, an injurious yielding of the material surrounding the aperture for the insertion of the holding members of the tooth to be inserted makes itself notice able. This yielding is particularly noticeable at the slot apertures of back plates for sliding teeth, since here the margins of the slots are in direct contact with the pin of the tooth which takes up the chewing. pressure.

It has already been proposed to make the back plate of two sorts of gold, a harder and therefore more resistant sort for the side of the slot and a softer sort for the rear side.

The necessary soldering together of different gold plates, however, considerably increases the cost of a back plate, because the part to be mounted and soldered had to be made completely and throughout the size of the 'plate of harder and more expensive gold, merely in order to obtain more resistant slot margins.

With that end in view attempts have been made to produce the part of the back plate so surrounding the insertion aperture for the tooth separately as a little box or alveolus, while the remaining part, which bears snugly against the porcelain back of the tooth, was modeled in wax and then cast in gold. This method of production by casting never resulted in an accurate bearing of the golden part of the little plate against the porcelain. back of the tooth and was therefore given up by technologists The making of these back plates had to be attended to by the dental mechanic himself in every individual case, whereas the back plate according to the present invention can be delivered ready for use by the manufacturer for the artificial teeth known as knob and plate cramp teeth with one or two pins. And since these factory-made back plates prove not only more reliable but also cheaper, the main object of'the individual production formerly customary, that of cheapness, with the 381,326, and in Germany April 22, 1929.

undesirable accessory phenomena (poor bear- 7 ing of the metal surface on the porcelain surface, and tearing out of the tooth anchoring) disappears.

According to plate comprises: an insertion piece with an aperture for the reception of the tooth-securing members, and the halves of the remainder of the back plate, which is divided in two parts, the insertion piece being lodged in a recess in the latter. Moreover the process for the manufacture of these back plates ensures a permanent union of the parts with one another.

The accompanying drawing shows a few constructional examples of the invention.

Figure 1 shows the first example in front elevation.

- Figure 2 in rear elevation, and

Figure 3 in sectional elevationthrough the entrance aperture, the position of the secured tooth being illustrated for the purpose of making the method of using the plate clear.

Figured shows the plate taken to pieces.

Figures 5 to 8 illustrate two further forms of the invention, each in front elevation, with its associated insertion piece, the shape of the corresponding tooth being indicated in the plan. i

In the three-part tooth back plate, illustrated by the Figures 1 to 4 a is the insertion piece for the reception of the tooth, and consisting of harder material than the remainder of the plate, and b and c are the remaining parts of the back plate, of 18 carat gold for instance, which are complementary to one another and are intended for the reception of the insertion piece. d denotes the introducing slot in the insertion piece, which, as in the known back plates for single-pin teeth, consists of a widened part for the entrance of the little plate 6 and of a passage f connected therewith for guiding the neck of the little plate of the tooth g, and opens into the usual cavity hintended for supporting the little plate 6. The margins of the insertion piece a are beveled from the slot side rearwards. Corresponding to the periphery of the insertion piece, recesses in the halves b and c of the back platenform when assembled a chamber 2',

the invention the tooth back which has to receive the insertion piece. In order to obtain enough room for the chamber,

the back plate projects backwards at the effected by fitting the halves together, after fitting in the insertion piece, and soldering the contact surfaces of the halves. On account of the e?- eled edges the insertion piece can no longer drop out, and it is deprived of any possibility of moven'ient by the halves of back plate accurately bearing upon it, as a result of which the tooth also is immovably fixed. Thanks to the employment of harder material for the insertion )ieoe a tearing out of the margins of ti rlot therein is rendered impossiblc. fastened, only the After the tooth latter and the parts of the back plate that are made of precious metal are visible.

According to the stress the raised back portion of the plate would he e to be strength cned, which can be done for instance by mixing platinum or iridium with the gold layer. As further base materials for the insertion piece there comes into question asbestos cement slate, magnalium and others, since, as will be evident from what has been stated, in the choice of the material for the insertion piece, one is bound not to the appearance but only to the nature thereof, to the employment of hard material. As precious metals there come into question 8 to Ll carat gold and in special cases platinized gold. The insertion piece, and with it the back plate, may therefore be delivered as desired in cheaper or dearer but in any case more resistant construction than has hitherto been the case. The tooth set in the back plate may be cemented in but if the parts are constructed accurately this is not necessary. Besides the clamping as described, the insertion piece, insofar as it is made of precious metal, may be completely soldered in, that is to say, inseparably connected with the remainder of the plate.

Furthermore the insertion piece may be welded to the metallic portions of the back plate.

In the constructional form illustrated by Figures and 6 the aperture for the introduction of the tooth into the insertion piece is elliptical and is particularly intended for teeth with socalled knob cramps, which are cemented in. This construction is usual, under the name of box tooth, in bridge work. Figures 7 and 8 show an insertion piece with two keyhole-shaped introduction slots Z for the tooth. In other respects the construction of the back plate is the same as in the example previously described.

Vhat I claim is:

1. A back plate for artificial teeth composed of two plate sections the meeting edges of which are provided with a recess, and an insertion piece having an aperture for the reception of toothed securing members and lodged in the recess when the plate sections are assembled.

2. A back plate forartificial teeth composed of a pair of complemental sections provided attheir meeting edges with a recess, and an insertion piece having an aperture for the reception of toothed securing members and lodged in the recess at the time the sections a re assembled, the edges of the insertion piece and the edges of the recess being dove-tailed to prevent the insertion piece from dropping out.

In testimony whereof I have signed my name to this specification.

h [AXIMILIAN DE TERRA. 

